Alternate period changes in close binary systems.

A model in which small stellar structure fluctuations result in the short term alternate period changes observed in detached and semidetached binary systems is investigated. The quadrupole moment fluctuations of about 15 percent for the case of Algols may be due to a variation in stellar radius of about 3 percent, an apsidal motion constant variation of about 15 percent, or, more realistically, a combination of both phenomena. In contrast to mass transfer or mass loss explanations, the present model is compatible with the absence of any significant long term period changes in Algols and cataclysmic variables, with the fact that Algols are in the slow nuclear phase of mass transfer, and with similar short term period changes observed in detached systems. Mechanisms are discussed that could cause fluctuations in